// 来自：
// https://aceld.gitbooks.io/libevent/content/32_epollde_fan_ying_dui_mo_shi_shi_xian.html

#include <stdlib.h>
#include <stdio.h> 
#include <stdio.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#define MAX_EVENTS  1024
#define BUFLEN 128
#define SERV_PORT   8080


/*
 * status:1表示在监听事件中，0表示不在 
 * last_active:记录最后一次响应时间,做超时处理
 */
struct myevent_s {
    int fd;                 //cfd listenfd
    int events;             //EPOLLIN  EPLLOUT
    void *arg;              //指向自己结构体指针
    void (*call_back)(int fd, int events, void *arg);
    int status;             // 该 myevent_s 对象是非被使用的标志
    char buf[BUFLEN];
    int len;
    long last_active;
};

int g_efd;          /* epoll_create返回的句柄 */
struct myevent_s g_events[MAX_EVENTS+1];   /* +1 最后一个用于 listen fd */

void eventset(struct myevent_s *ev, int fd, void (*call_back)(int, int, void *), void *arg)
{
    ev->fd = fd;
    ev->call_back = call_back;
    ev->events = 0;
    ev->arg = arg;
    ev->status = 0;
    //memset(ev->buf, 0, sizeof(ev->buf));
    //ev->len = 0;
    ev->last_active = time(NULL);

    return;
}

void recvdata(int fd, int events, void *arg);
void senddata(int fd, int events, void *arg);

/* efd : epoll fd*/
void event_add(int efd, int events, struct myevent_s *ev)
{
    struct epoll_event epv = {0, {0}};
    int op;
    epv.data.ptr = ev;
    epv.events = ev->events = events;

    if (ev->status == 1) {
        op = EPOLL_CTL_MOD;
    } 
    else {
        op = EPOLL_CTL_ADD;
        ev->status = 1;
    }

    if (epoll_ctl(efd, op, ev->fd, &epv) < 0)
        printf("event add failed [fd=%d], events[%d]\n", ev->fd, events);
    else
        printf("event add OK [fd=%d], op=%d, events[%0X]\n", ev->fd, op, events);

    return;
}

void event_del(int efd, struct myevent_s *ev)
{
    struct epoll_event epv = {0, {0}};

    if (ev->status != 1)
        return;

    epv.data.ptr = ev;
    /* 收回 myevent_s 对象 */
    ev->status = 0;
    epoll_ctl(efd, EPOLL_CTL_DEL, ev->fd, &epv);

    return;
}


void accept_conn(int lfd, int events, void *arg)
{
    struct sockaddr_in cin;
    socklen_t len = sizeof(cin);
    int cfd, i;

    if ((cfd = accept(lfd, (struct sockaddr *)&cin, &len)) == -1) {
        if (errno != EAGAIN && errno != EINTR) {
            /* 暂时不做出错处理 */
        }
        printf("%s: accept, %s\n", __func__, strerror(errno));
        return;
    }

    /* 为新连接分配在 myevent_s 类数组 g_events 中分配一个对象 */
    do {
        for (i = 0; i < MAX_EVENTS; i++) {
            if (g_events[i].status == 0)
                break;
        }

        if (i == MAX_EVENTS) {
            printf("%s: max connect limit[%d]\n", __func__, MAX_EVENTS);
            break;
        }

        int flag = 0;
        if ((flag = fcntl(cfd, F_SETFL, O_NONBLOCK)) < 0)
        {
            printf("%s: fcntl nonblocking failed, %s\n", __func__, strerror(errno));
            break;
        }

        eventset(&g_events[i], cfd, recvdata, &g_events[i]);
        event_add(g_efd, EPOLLIN, &g_events[i]);
    } while(0);

    printf("new connect [%s:%d][time:%ld], pos[%d]\n", inet_ntoa(cin.sin_addr), ntohs(cin.sin_port), g_events[i].last_active, i);

    return;
}

void recvdata(int fd, int events, void *arg)
{
    struct myevent_s *ev = (struct myevent_s *)arg;
    int len;

    len = recv(fd, ev->buf, sizeof(ev->buf), 0);
    /* 撤销 epoll 对此事件的监控 */
    /* epoll 事件循环中，每次循环体执行之前要重新设置要监听的事件 */
    event_del(g_efd, ev);

    if (len > 0) {
        ev->len = len;
        ev->buf[len] = '\0';
        printf("C[%d]:%s\n", fd, ev->buf);
        /* 转换为发送事件 */
        eventset(ev, fd, senddata, ev);
        event_add(g_efd, EPOLLOUT, ev);
    }
    else if (len == 0) {
        close(ev->fd);
        /* ev-g_events 地址相减得到偏移元素位置 */
        printf("[fd=%d] pos[%d], closed\n", fd, (int)(ev - g_events));
    }
    else {
        close(ev->fd);
        printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));
    }

    return;
}

void senddata(int fd, int events, void *arg)
{
    struct myevent_s *ev = (struct myevent_s *)arg;
    int len;

    len = send(fd, ev->buf, ev->len, 0);
    //printf("fd=%d\tev->buf=%s\ttev->len=%d\n", fd, ev->buf, ev->len);
    //printf("send len = %d\n", len);

    event_del(g_efd, ev);
    if (len > 0) {
        printf("send[fd=%d], [%d]%s\n", fd, len, ev->buf);
        eventset(ev, fd, recvdata, ev);
        event_add(g_efd, EPOLLIN, ev);
    }
    else {
        close(ev->fd);
        printf("send[fd=%d] error %s\n", fd, strerror(errno));
    }

    return;
}

void init_listen_socket(int efd, short port)
{
    int lfd = socket(AF_INET, SOCK_STREAM, 0);
    fcntl(lfd, F_SETFL, O_NONBLOCK);
    eventset(&g_events[MAX_EVENTS], lfd, accept_conn, &g_events[MAX_EVENTS]);
    event_add(efd, EPOLLIN, &g_events[MAX_EVENTS]);

    struct sockaddr_in sin;

    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = INADDR_ANY;
    sin.sin_port = htons(port);

    bind(lfd, (struct sockaddr *)&sin, sizeof(sin));

    listen(lfd, 20);

    return;
}

int main(int argc, char *argv[])
{
    unsigned short port = SERV_PORT;

    if (argc == 2)
        port = atoi(argv[1]);

    g_efd = epoll_create(MAX_EVENTS+1);

    if (g_efd <= 0)
        printf("create efd in %s err %s\n", __func__, strerror(errno));

    init_listen_socket(g_efd, port);

    /* 事件循环 */
    struct epoll_event events[MAX_EVENTS+1];

    printf("server running:port[%d]\n", port);
    int checkpos = 0, i;
    while (1) {
        /* 超时验证，每次测试100个链接，不测试listenfd 当客户端60秒内没有和服务器通信，则关闭此客户端链接 */
        long now = time(NULL);
        for (i = 0; i < 100; i++, checkpos++) {
            if (checkpos == MAX_EVENTS)
                checkpos = 0;
            if (g_events[checkpos].status != 1)
                continue;
            long duration = now - g_events[checkpos].last_active;
            if (duration >= 60) {
                close(g_events[checkpos].fd);
                printf("[fd=%d] timeout\n", g_events[checkpos].fd);
                event_del(g_efd, &g_events[checkpos]);
            }
        }
        /* 等待事件发生 */
        int nfd = epoll_wait(g_efd, events, MAX_EVENTS+1, 1000);
        if (nfd < 0) {
            printf("epoll_wait error, exit\n");
            break;
        }
        for (i = 0; i < nfd; i++) {
            struct myevent_s *ev = (struct myevent_s *)events[i].data.ptr;
            if ((events[i].events & EPOLLIN) && (ev->events & EPOLLIN)) {
                ev->call_back(ev->fd, events[i].events, ev->arg);
            }
            if ((events[i].events & EPOLLOUT) && (ev->events & EPOLLOUT)) {
                ev->call_back(ev->fd, events[i].events, ev->arg);
            }
        }
    }

    /* 退出前释放所有资源 */
    return 0;
}